Electric discharge device



INVENTOR H. J". D/f/LE'V.

BY RNEY fi v ATTO H. J. DAILEY ELECTRIC DISCHARGE DEVICE Filed June 29, 1951 Jan. 20, 1953 Patented Jan. 20, 1953 ELECTRIC DISCHARGE DEVICE Hampton J. Dailey, Verona, N. J., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application June 29, 1951, Serial No. 234,215

4 Claims.

This invention relates to electrical dischar tubes, and in particular relates to a lead-in for conducting heating current to thermionically emissive cathodes, more particularly in the case of tubes operating at very high frequencies.

Electrical discharge tubes present a problem of considerable difiiculty in providing lead-ins for the above-mentioned purpose which shall maintain a fixed and accurately positioned support for the cathode structure or parts despite the expansion incident to heating and cooling, which must be even, and which shall have a low impedance in the case of higher frequencies. The structure here disclosed attains such properties by employing lead-ins in the form of hemi-cylinders of suitable metal sealed through the walls of the tube.

In general, therefore, the object of this invention may be described as the provision of improved lead-ins for thermionic cathodes in electrical discharge tubes.

More specifically, the object may be described as the provision of lead-ins for thermionic cathodes which will accurately position and help support the latter.

Another object is to provide cathode lead-ins and supports which will produce little displacement of the cathode due to expansion by heating of the latter.

Still another object is to provide cathode leadins which shall have a low impedance to highfrequency alternating currents.

Other objects of the invention will become evident, both by express description and by implication frcm the following description taken in connection with the drawings in which the same reference numerals are used to denote the same elements in the different figures.

Fig. l is a view in elevation, and partly in section, showing the portion of an electron tube, in which the invention is embodied;

Fig. 2 is a sectional plan view along the line IIII of Fig. 1; and

Fig. 3 is a sectional plan looking at the top of Fig. 1.

Referring in detail to the drawings, the wall of an electrical discharge tube I, preferably of borosilicate glass, has sealed through it two metal hemicylinders 2 and 3 which may, at the region where the wall I is sealed to them, be of the cobalt-nickel-iron alloy known as Kovar, as described in Howard Scott Patent No. 2,062,335 of December 31, 1936, or of any other metal sealing satisfactorily to wall I. The hemicylinders 2 and 3 are insulated from each other by gaps 3A,

and the glass of wall I extends through these gaps to link up with a tubulation ll sealed to the internal faces of the hem-icylinders 2 and 3 and extending downward inside them to afford a duct through which they, together with the complete envelope of which wall I is a major part, may be exhausted in ways well known in the vacuum tube art. The upper end of the tubulation 4 is provided with a perforated metal cap 5, which supports a post 6 extending upward along the axis of the discharge tube to support the upper end of the cathode and other conventional electrodes (not shown).

The upper end of hemi-cylinder 2 extends above that of hemi-cylinder 3 and is attached to a short annular cap or crown, herein referred to as outer crown 1, having upwardly-extending fingers 8 spaced at equal intervals about its circumference. The hemi-cylinder 3 is attached at its upper end to a cap or crown, herein referred to as inner crown 9, having an outside diameter less than that of outer crown I so that crowns 1 and 9 are separated and insulated from each other by an annular gap. The portions of inner crown 9 which are overlapped by the upper end of hemicylinder 2 are cut away or bent inward so as not to contact hemi-cylinder 2 or outer crown l. The upper edge of inner crown 9 is provided with upwardly extending fingers l I, preferably positioned circumferentially midway between the angular positions of fingers 8 of the outer crown 1.

The thermionic cathode of the tube comprises an even number of filamentary members, which may be the legs of hairpin-filaments for example, alternately fastened to the fingers 8 and II. Thus, heating current may fiow from a supply circuit through hemi-cylinder 2, outer crown 1 and fingers 8 up one set of filaments, then down the other set through fingers ll, inner crown 9 and hemi-cylinder 3 back into the supply circuit. The upper ends of the filaments I 2 may be attached to any suitable support (not shown) in ways well known in the art.

The hemi-cylindrical form of members 2 and 3 and the close spacing between their adjacent straight edges facilitates their accurate positioning and rigid maintenance of the positioning of cathode filaments l2. Their large surface area and substantially equal size insures equality of their temperatures, and equality of expansion. Furthermore, their large ratio of surface to crosssection minimizes or reduces their impedance in crease due to skin effect of high-frequency currents and also lowers self-inductance. The arrangement is thus excellently adapted to the requirements of high-frequency lead-ins. While the principles of the invention have been illustrated by application to a, cathode supplied through two lead-ins, they are equally adapted to three-phase or other polyphase-supplied cathodes by modification which will be evident to those skilled in the art.

1. In'cembinationwith an enve'lope of an electrical discharge device, a pair of hemi-cylindrical metal lead-ins coaxially positioned and sealed through the wall thereof, a first annular metal cap afiixed to one end of said lead-in, a second annular metal cap afiixedtothe-other -'said leadin and means to attach filament-ends to said caps.

2. In combination with the envelope of anelectrical discharge device, a pair of hemi-cylindrical metal lead-ins coaxially positioned and :sealed through the wall thereof, a first annular metal in, means to attach filament-Lends to said caps,

and a tubulation with-in'and sealed to the inner walls of said pair of lead-ins.

3. In combination with a cathode having an even number of filament legs and means for supporting one end of each of said legs, a pair of hemi-cylindrical metal lead-ins each connected to one-half of the other ends of said legs.

4. In combination with a cathode having an even number of filament legs and means for supporting one end of each of said legs, a pair of hemi-cylindrical metal lead-ins each connected to one-half of the other ends of said legs by an annular metal cap, said caps being spaced apart from each other at all points.

HAMPTON J. DAILE'Y.

:REFERENCES CITED The following :references are of record in the 'file or this patent:

UNITED STATES PATENTS Number Name Date 728,060 Whipple V iMaY"12, 1903 1,836,029 I-Iarase *Dec.'15, 1931 $468,433 Eitel et a1. Apr. 26, "1949 

